Defect structures in the silver halides

Abstract

We report a state of the art density functional theory study of the intrinsic defects within the rocksalt-structured silver halides. These materials are well known to favor Frenkel defect pairs over Schottky pairs---a key factor in their use as photographic materials. We report the defect structures and formation energies of the elementary point defects obtained using the supercell approximation. In agreement with recent experimental results, we find that the interstitial cation adopts a split-interstitial configuration, centered on a lattice site. The effects of electron or hole trapping on the defect centers in $\mathrm{AgCl}$ and $\mathrm{AgBr}$ are reported, including the formation energetics, structures, and spin localizations. Although limitations in the supercell method are evident, we have nevertheless obtained valuable new insights into the properties of these fascinating materials.